package com.xiaotu.lambda.java4;

import org.junit.Test;

import java.util.Optional;

/**
 * Optional类：为了在程序中避免出现空指针异常而创建的。
 *
 * 常用的方法：ofNullable(T t)
 *           orElse(T t)
 *
 * @author 张晓
 * @create 2021-06-29 16:14
 */
public class OptionalTest {

    /**
     * Optional.of(T t):创建一个Optional 实例，t 必须非空：
     * Optional.empty():创建一个空的Optional 实例
     * Optional.ofNullable(T t):t可以为null
     */
    @Test
    public void test1() {
        Girl girl = new Girl();
        Optional<Girl> optionalGirl = Optional.of(girl);
    }

    @Test
    public void test2() {
        Girl girl = new Girl();
        girl = null;
        Optional<Girl> optionalGirl = Optional.ofNullable(girl);
        System.out.println(optionalGirl);

        //orElse(T t1):如果当前的Optional内部封装的t 是非空的，则返回内部的t
        //如果内部的t是空的，则返回orElse()方法中的参数t1

        Girl girl1 = optionalGirl.orElse(new Girl("赵丽颖"));
        System.out.println(girl1);

    }

    public String getGirlName(Boy boy) {
        return boy.getGirl().getName();
    }

    @Test
    public void test3() {
        Boy boy = new Boy();
        String girlName = getGirlName(boy);
        System.out.println(girlName);
    }

    //优化以后的getGirlName():
    public String getGirlName1(Boy boy) {
        if (boy != null) {
            Girl girl = boy.getGirl();
            if (girl != null) {
                return girl.getName();
            }
        }
        return null;
    }

    @Test
    public void test4() {
        Boy boy = new Boy();
        boy = null;
        String girlName = getGirlName1(boy);
        System.out.println(girlName);
    }

    //使用Optional类的getGirlName():
    public String getGirlName2(Boy boy) {
        Optional<Boy> boyOptional = Optional.ofNullable(boy);
        Boy boy1 = boyOptional.orElse(new Boy(new Girl("迪丽热巴")));
        Girl girl = boy1.getGirl();
        Optional<Girl> optionalGirl = Optional.ofNullable(girl);
        Girl girl1 = optionalGirl.orElse(new Girl("古力娜扎"));
        return girl1.getName();
    }

    @Test
    public void test5() {
        Boy boy = null;
        boy = new Boy();
        String girlName2 = getGirlName2(boy);
        System.out.println(girlName2);
    }

}
